Feb 3 (Reuters) - Russia's monthly budget revenues from oil and gas fell in January to their lowest level since August 2020 under the impact of Western sanctions on its most lucrative export, Finance Ministry data showed on Friday. Monthly tax and customs revenue from energy sales declined 46% in a year - reflecting the fact that, while the price of the global benchmark Brent blend was little changed, the average monthly price of Russia's Urals blend was down 42%, according to the ministry. See here for a complete list of exchanges and delays